This invention relates to glazing panels and particularly, but not exclusively, to solar control and/or low emissivity glazing panels which are intended to undergo heat treatment following application to the glazing substrate of an optical filter in the form of a coating stack.
The invention relates more particularly to cases where a coating stack is applied to the glazing by a vacuum deposition technique, for example by sputtering or magnetron sputtering.
Multiple factors must be considered when designing coating stacks for glazing applications. These incdude not only the desired opto-energetic performance of the coated glazing panel but also, for example, the abrasion resistance of the coating stack (to facilitate handling and processing), the stability and chemical durability of the coating stack (to facilitate storage under various conditions) and the tolerances of the control of the manufacturing process (to facilitate acceptable manufacturing yields and consistency between product runs).
It is known to apply a top coat to a coating stack particularly in an attempt to increase the abrasion resistance and/or chemical durability of a coatings stack The use of metallic layers (for example of chromium, nickel chromium or zinc) or dielectric layers (for example titanium oxide, silicon oxide, zinc oxide, silicon nitride, aluminium nitride) has been proposed in this context. However, many known non-metallic top coats suffer from insufficient chemical durability, whilst known metallic top coats can have a number of disadvantages.